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There seems to be conflicting information on the internet.

Are super capacitors polarized? For instance, could you charge them and then suddenly invert their polarity (à la charge pump)?

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  • \$\begingroup\$ Super capacitors are polarised. \$\endgroup\$ – user19579 Apr 15 '14 at 6:02
  • \$\begingroup\$ A charge pump can be made with polarized capacitors. \$\endgroup\$ – Wouter van Ooijen Apr 15 '14 at 6:40
  • \$\begingroup\$ wikipedia (shitty source i know!) article on supercaps en.wikipedia.org/wiki/Supercapacitor says "Supercapacitors are polarized and must operate with the correct polarity. Polarity is controlled by design with asymmetric electrodes, or, for symmetric electrodes, by a potential applied during manufacture." And charge pumps are not really inverting the polarity, the caps are switched to be in series giving a higher voltage. Maybe you mean inverting charge pumps for negative voltage? \$\endgroup\$ – KyranF Apr 15 '14 at 6:59
  • \$\begingroup\$ @kyran even those can be made with polarized capacitors, check for unstance the max232. \$\endgroup\$ – Wouter van Ooijen Apr 15 '14 at 7:07
  • \$\begingroup\$ @WoutervanOoijen yes, i've used them in my designs. Although for PCB space I used non-polarized ceramic caps \$\endgroup\$ – KyranF Apr 15 '14 at 7:09
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From wikipedia:

Supercapacitors are polarized and must operate with the correct polarity. Polarity is controlled by design with asymmetric electrodes, or, for symmetric electrodes, by a potential applied during manufacture.

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Polarity

Although the anode and cathode of symmetric supercapacitors consist of the same material, theoretically supercapacitors have no true polarity. Normally catastrophic failure does not occur, however reverse-charging a supercapacitor lowers its capacity. It is recommended practice to maintain the polarity resulting from a formation of the electrodes during production. Asymmetric supercapacitors are inherently polar.

Supercapacitors may not be operated with reverse polarity, precluding AC operation.

In other words, even for capacitors with symmetric electrode structures, there is a "charging" process during the manufacture that creates a asymmetric insulating layer inside the capacitor. You can reverse-charge a super capacitor, but doing so likely leads to a microscopic degradation of the specially prepared electrode surfaces (probably due to bizarre chemistry physics I don't understand), reducing the available capacitance.

I suspect this is similar to the process for manufacturing lead-acid batteries, where the plates are actually initially identical, and the initial charging process modifies the chemical properties of both plates. In their un-conditioned state, it's probably possible to electrochemically convert either electrode to the "positive" electrode, but once the electrode have been conditioned, trying to reverse their polarization would probably damage their chemical properties, and thus the capacitor.

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